Operator-protective shield

ABSTRACT

A COMBINATION GUARD DESIGN FOR HIGH-SPEED CUTTING TOOLS, ESPECIALLY GRINDING WHEELS, CONSISTING OF TWO PORTIONS THAT TELESCOPE TOGETHER, THE AFT CONVENTIONAL PORTION IS THE STANDARD GRINDING WHEEL GUARD WHICH IS ATTACHED TO AND RECIPROCATES WITH THE WHEELHEAD OR WHEEL SLIDE, THE FORWARD PART IS AN OPERATOR-PROTECTIVE SHIELD (COMPRISED BASICALLY OF A MAIN FRAME, AT LEAST ONE SIDE COVER AND A REPLACEABLE GUARD SEGMENT WITH A DEFINITE SIZE WORKPIECE OPENING), FIXEDLY SECURED TO THE MACHINE BASE OR FRAME AND IN OVERLAPPING RELATION WITH THE STANDARD GRINDING WHEEL GUARD IN ALL OPERATING POSITIONS OF THE WHEEL SLIDE, SAID COMBINATION IN THE EVENT OF GRINDING WHEEL FAILURE SUBSTANTIALLY COMPLETELY PREVENTING BROKEN WHEEL FRAGMENTS FROM LEAVING THE GRINDING MACHINE AND CAUSING INJURY TO THE OPERATOR.

Feb.23, 1971 Y EK ETAL- 3,564,780

I OPERATOR-PROTECTIVE SHIELD Filed May -e, "1969' r I 2 Sheets-Sheet 1 INVENTORS ROLF T. GRYZMEK HOWARD W. RENNER AQW ATTORNEYS Feb. 23,1971 RZ MEK ET AL 3,564,780

OPERATOR-PROTECTIVE SHIELD Filed May 6. 1969 2 sheetsesheet 2 United States Patent 3,564,780 OPERATOR-PROTECTIVE SHIELD Rolf T. Grzymek, Cincinnati, and Howard W. Renner,

Wyoming, Ohio, assignors to Cincinnati Milacron Inc.,

Cincinnati, Ohio, a corporation of Ohio Filed May 6, 1969, Ser. No. 822,119 Int. Cl. B24b 55/04 US. Cl. 51--269 Claims ABSTRACT OF THE DISCLOSURE A combination guard design for high-speed cutting tools, especially grinding wheels, consisting of two portions that telescope together; the aft conventional portion is the standard grinding wheel guard which is attached to and reciprocates with the wheelhead or wheel slide; the forward part is an operator-protective shield (comprised basically of a main frame, at least one side cover and a replaceable guard segment with a definite size workpiece opening), fixedly secured to the machine base or frame and in overlapping relation with the standard grinding wheel guard in all operating positions of the wheel slide, said combination in the event of grinding wheel failure substantially completely preventing broken wheel fragments from leaving the grinding machine and causing injury to the operator.

BACKGROUND OF THE INVENTION This invention relates to high-speed cutting tool guards, especially guards for high-speed grinding wheels.

With the advent of high-speed grinding the energy of the grinding wheel, or any given fragment thereof, is much higher at high speed, more exactly, it is 3.41 times as high at 12,000 f.p.m. (feet per minute) as at the conventional speed of 6,500 f.p.m. This, of course, implies greater danger to operating personnel and personnel safety during wheel blow-up can only be assured by adequate control of the wheel fragments. Since the traditional, generally circular, wheel guard design is far from an optimum design, it can be concluded that fragment escape cannot be negated without substantially enclosing the work-wheel contact zone.

SUMMARY OF THE INVENTION In accordance with this invention, a new guard design provides the operator with much more protection from grinding wheel fragments in the event of grinding wheel failure. It consists of two pieces that telescope together; the aft conventional portion is the standard grinding wheel guard which moves with the wheelhead and covers about 60% of the grinding wheel; the forward part is an operator-protective shield which is stationary and covers a substantially equal amount of the grinding wheel.

The following advantages of the operator-protector shield in combination with the standard grinding wheel guard exist for each of the major sources of personnel danger.

(a) fragment penetration: the operator-protective shield can easily be over-designed to any desired degree, by using either armor plate or increased thickness of boiler plate.

(b) hood problems: elimination of the hood (generally attached to the front upper portion of the standard grinding wheel guard) makes safety independent of its adjustment by the operator. In addition, failure of thehood fasteners -(e.i., the hood becoming a projectile) is eliminated as a danger.

(c) rotation of guard into the work area: the operatorpiotective shield acts as a second line of defense if the fasteners on a standard grinding wheel guard fail.

(d) fragment escape: over-design with respect to penetration and fastening allows a design aimed solely at breaking up wheel fragments, absorbing their energies, and tunneling them into a safe direction.

In summary, this invention provides an operator-protective shield especially suited for use with the standard wheel guard of a grinding machine having a support or base with ways and a movable wheelhead thereon for mounting the rotatable grinding wheel. The operatorprotective shield includes a main plate, fixedly secured to the machine base substantially normal to the movement of the wheelhead and having a frontal opening; at least one side cover fixedly secured to the machine base, substantially parallel to the movement of the wheelhead, with the main plate and side cover being secured so as to be in partially overlapping relation with the grinding wheel guard; and a replaceable guard segment, fixedly but removably secured to the main plate and fitting at least partially within the main plate front opening, and having an arcuate wall portion curved in approximate correspondency with the grinding wheel periphery, with the arcuate wall portion having a definite size opening therein to permit insertion of at least part of the workpiece to be machined. In addition, a deflection member may be movably attached to the main frame for selectively covering and uncovering the predetermined workpiece opening and the replaceable guard segment may be provided with a passage and a coolant nozzle for directing coolant between the grinding Wheel and the work. Furthermore, the lower arcuate wall portion of the replaceable guard segment may be formed so as to channel broken wheel segments into the base of the machine with the base, which also serves as a coolant reservoir, dissipating at least part of the energy of the broken wheel fragments being channelled thereto and helping to retain a substantial number of the wheel fragments.

BRIEF DRAWING DESCRIPTION FIG. 1 is a perspective view showing the location of the elements of this invention in relation to a grinding machine wheelhead.

FIG. 2 is a sectional view taken along line 2--2 of FIG. 1.

FIG. 3 is an exploded view of this invention.

FIG. '4 is a sectional view of a modified embodiment of this invention.

DETAILED DESCRIPTION Referring now to the drawings in detail, FIG. 1 shows a center type grinding machine 10 having a support or base 12 with a way portion 13 for slidingly receiving movable wheel slide 14. Wheelhead or cutting tool slide 14 has mounted in it, on suitable bearings (not shown), a grinding wheel spindle (not shown) to one end of which is fixedly attached a grinding or cutting wheel 16 and the other end of which (not shown) is suitably connected, in any of the ways well-known in the art, to drive motor 18, for rotating grinding wheel 16. Also attached to wheel slide 14 is grinding wheel guard 20 which partially envelopes grinding wheel 16. This being a center type grinding machine, it also includes a table portion 22 attached to or forming part of base 12 which further includes a slide 23 movably carrying a power driven headstock 24 and footstock 25 having centers 26 and 27, respectively, for supporting the work (not shown) to be ground.

The general construction of operator-protective shield 28 of this invention can best be seen by reference to FIGS. 2 and 3 which show it to be comprised of three main portions namely main frame or plate 30, side cover 62, and replaceable guard segment or insert 84. Forming part of main frame 30, as best shown in FIG. 3, is

center frame 32 having generally vertical front wall portion 34 with front wall opening 36 and a plurality of holes 37; upper, generally horizontal, rearwardly extending portion 38; and lower, generally horizontal, rearwardly extending portion 40 having multiple holes 42 to, for example, allow for fastening center frame 32 to machine base 12 by means of bolts 44 as best shown in FIG. 2. Other parts of main frame 30 are side frames 46 and 48 which, although shown removed from center frame 32 in the exploded view in FIG. 3 for the sake of clarity, are in actual practice securely welded thereto, thus resulting in very strong main frame 30. Side frame 46 on its lower rearwardly extending portion 52 has a plurality of holes 54 to allow for fastening main frame 30 to another part of machine base 12 by means of, for example, bolts 55 as best shown in FIG. 2. Side frame 48 which has a scalloped rear portion 56 also has a plurality of threaded holes 58 and two hinge collars 60.

Mating with hinge collars 60 on main frame 30 and secured by hinge pins 70 are hinge collars 68 of side cover 62 having generally vertical body portion 64 and generally horizontal foot portion 66, the former having a plurality of threaded holes 72 corresponding in location to threaded holes 58 on side face 48 of main frame 30, thus allowing attachment of side cover 62 to main frame 30 by means of multiples of bolts 74. A series of holes 78 in foot portion 66 also permits the fastening of side cover 62 directly to machine base 12 by means of, for example, bolts 80. Based on the above description it should be evident that upon the removal of bolts 74 and 80 side cover 62 may be pivoted from the position shown in FIG. 1 to facilitate removal of grinding wheel 16 whenever this is desired.

Attached to the rear surface of vertical front wall portion 34 of center frame 32 is replaceable guard segment or member 84 having mounting portion 86 with threaded holes 88 and forwardly extending arcuate or curved surface wall or segment portion 90 with side Walls 92 and scalloped or concave predetermined workpiece opening 94. Guard segment member 84 extends at least partially into main frame front wall opening 36 and member 84, whose threaded holes 88 correspond in location to holes 37 in center frame 32 of main frame 30, is attached to main frame 30 by means of multiples of bolts 96.

As may best be seen in FIG. 1 curved surface wall portion 90 of replaceable guard segment 84 is shaped in similar correspondency with the periphery of grinding wheel 16 so that part of the latter, in operation during the grinding process, actually rotates into or through front Wall opening 36 in main frame 30.

In operation, the workpiece to be ground (not shown) is rotatably carried between center 26 and 27 respectively, and extends into concave workpiece opening 94 in replaceable guard segment 84. Replaceable guard segment 84 and workpiece opening 94 are designed and constructed so as to fit the particular workpiece to be ground and may well be irregular in shape such being the case if a workpiece or part for example, requires simultaneous grinding of several ditferent diameters. Replaceable guard element 84 is, as its name implies, replaceable and must be replaced when workpieces of different sizes or shapes are to be ground. Replaceable guard segment 84 is therefore custom designed and constructed for each particular size and shape of workpiece, with workpiece opening 94 being made just large enough to freely accommodate the workpiece to be ground. This minimum exposure of the grinding wheel of course adds materially to the safety of the operator and the cost of the individual replaceable guard segments is a negligible factor when compared to the increase in operator safety and increase in production obtained by the use of higher wheel speeds which this invention allows.

As shown in FIG. 1 operator-protective shield 28, which is basically composed of main frame 30 and side frames 46, 48, side cover 62 and replaceable guard segment 84, is at all times fixedly secured to machine base 12 by multiples of bolts 44, 55, and 80. Regardless of the posi tion of movable tool slide 14, to which grinding Wheel guard 20 is fixedly secured, operator-protective shield 28 and grinding wheel guard 20 are always in overlapping or telescoping relationship with respect to each other since each covers about 60% of grinding wheel 16. During the grinding process, slide 14, which is reciprocable in a direction substantially normal to center frame front wall portion 34 (and thus to the workpiece), is moved forward until grinding wheel 16 engages the rotatably supported workpiece (between centers 26, 27) extending into concave workpiece opening 94. Except for the projected area of the workpiece, which substantially corresponds to the area of workpiece opening 94, the entire surface of grinding wheel 16 is completely covered by the combination of grinding wheel 20 and operator-protective shield 28. Thus, operator-protective shield 28, by being fixedly secured to machine base 12 and being at all times, regardless of the position of wheel slide 14 in telescoping relation with grinding wheel guard 20 in the event of failure of grinding wheel 16 substantially completely prevents broken wheel fragments from leaving grinding machine 10 and causing injury to the grinding machine operator,

FIG. 4 is a sectional view of a further embodiment of this invention utilizing a modified replaceable guard segment 132, and like numerals are used on parts similar to those shown in FIGS. 1 to 3. Basically, operator-protective shield 128 of FIG. 4 is also comprised of three main portions, namely, main frame 30, side cover 62 (not shown), and replaceable guard segment or insert 132.

Pivotally mounted at 102 to bracket 104, attached to upper generally horizontally rearwardly extending portion 38 of main frame 30, is an actuating cylinder 106 Whose piston rod 108 is movably pinned at 112 to one end 116 of crank arm 114. Crank arm 114, which is pivotally attached to main frame portion 38 at 120, has its other end 118 pivotally attached at 122 to one end of substantially vertically disposed deflection member 126, the other end of which selectively covers or uncovers the workpiece opening in replaceable guard segment 132 depending upon the actuation of cylinder 106. The addition of deflection member 126 to operator-protective shield 128 gives added operator protection by providing a deflection means for the workpiece which, if hit by Wheel fragments during a grinding wheel failure, can act as a projectile. The necessary control elements for actuating cylinder 106 (for raising or lowering deflection member 126) may for example be readily incorporated into the machine control circuit to automatically lower deflection member 126 at the start of the grinding cycle and automatically raise it at the end of the cycle.

Attached to the rear surface of vertical front wall portion 34 of main frame 30 and extending into front wall opening 36 is replaceable guard segment 132 composed of mounting bracket 134, inwardly extending curved surface wall portion 136, front plate 138, two side plates 140, workpiece cradle 174, and coolant line 144.

Mounting bracket 134, having substantially fiat portion 146 with multiple threaded holes 148, also has inwardly depending length portions 152 to the ends of which inwardly extending or convex curved or arcuate surface wall portion 136 is fixedly secured. Mounting bracket 134, whose holes 148 correspond in location to holes 37 in main frame 30, is attached thereto by means of multiples of bolts 96. Curved surface wall portion 136, which is generally shaped in similar correspondency or conformity with the grinding wheel periphery, has its upper end 154 extended so as to closely approach the inside surface of grinding Wheel guard 20 while its lower end 156 is angled so as to aid in channeling grinding wheel debris into a cavity in base 12 of grinding machine 10 in the event of grinding wheel failure.

Curved surface wall portion 136 is also provided with an opening 158 defined as the space between upper and lower inner wall ends 160, 162 respectively, running the entire width of wall portion 136 which by necessity of course, must be at least as wide as the grinding wheel being utilized. Opening 158 roughly corresponds to opening 166, defined as the space between upper and lower inner wall ends 168, 170, respectively, of front plate 138 which is rigidly secured on its upper and lower extremities to mounting bracket fiat portion 146. Front plate 138 and curved wall portion 136, which both have the same width dimensions, are joined on their side faces by end plates 140 rigidly and sealingly secured thereto. Lower inner wall ends 162, 170 of curved wall portion 136 and front plate 138 respectively, are also rigidly and sealingly secured together and provide a base for-workpiece cradle 174, which provides support for workpiece 176 before and after the grinding operation, however, during the grinding operation, workpiece 176 is rotatably supported between centers 26 and 27. The space between workpiece cradle 174 and upper wall end 168 of front plate 138 effectively defines workpiece opening 172. Upper wall ends 160, 168 of curved surface wall portion 136 and front plate 138 respectively, are not joined but rather have an opening 178 there between formed so as to constitute a coolant nozzle. Coolant line 144 is attached to one of thes side plates 140 and feeds coolant into a cavity 182 defined by side walls 140, the upper part of front plate 138, curved wall portion 136, and mounting bracket 134. Coolant n'ozzle 178, therefore, becomes an integral part of replaceable guard segment 132 and is designed so as to channel the coolant directly into grinding zone 180 between grinding wheel 16 and workpiece 176.

As previously noted, the lower end 156 of curved surface wall portion 136 is angled so as to aid in channeling grinding wheel debris into a cavity 183 in base 12 of grinding machine in the event of grinding wheel failure. Cavity 183 in practice serves a triple function inasmuch as it provides a place for channeling wheel debris; it serves as a coolant reservoir; and coolant 184 helps to slow down the fragments thus not only dissipating at least part of the energy of the fragments but also protecting other machine components from ricocheting fragments.

In order to shield coolant 184 from contaminates during the normal operation of grinding machine 10 but in the event of grinding wheel failure to be able to absorb at least part of the energy of the wheel fragments, at least part of the top surface of coolant reservoir 182 consists of a yieldable cover means 186, for example a sheet metal plate.

The grinding operation involving the use of operator protective shield 128 is substantially similar to the previously described operation involving the use of operatorprotective shield 128 with the addition of deflection member 126 which selectively covers or uncovers workpiece opening 172 and thus in conjunction with grinding wheel guard 20 substantially totally shields the operator from both grinding wheel 16 and workpiece 176. Of course, replaceable guard segment 132 must again be replaced when workpieces of different sizes or shapes are ground. The necessary control elements for the actuating of cooling nozzle 178 may be readily incorporated into the machine control circuit to, for example, automatically starting coolant flow through cooling nozzle 178 just prior to the start of the grinding cycle, and automatically stopping it at the end of the cycle.

While the use of this invention is of special significance with respect to high-speed grinding, it will also provide significantly increased operator protection even at conventional wheel speeds.

While the invention has been described in connection with possible forms or embodiments thereof, it is to be understood that the present disclosure is illustrative rather than retrictive and that changes or modifications may be resorted to without departing from the spirit of the invention.

What is claimed is:

1. An operator-protective shield for a machine tool having a base with ways and a movable slide thereon for mounting a high speed rotatable cutting tool and a guard therefor, said shield comprising:

(a) a main frame, having a front wall opening, fixedly secured to the machine base substantially normal to the direction of movement of the cutting tool slide;

(b) at least one side cover fixedly secured to the main frame substantially parallel with the direction of movement of the cutting tool slide, with said main frame and side cover being secured so as to be in overlapping relation with said cutting tool guard in all operating positions of the cutting tool slide; and

(c) a replaceable guard segment fixedly secured to the main frame and extending at least partially into the main frame front wall opening, and having a definite size opening therein to permit insertion of the workpiece to be machined.

2. An operator-protective shield for a grinding machine having a base with ways and a movable wheelhead thereon for mounting a high speed rotatable grinding wheel and a grinding wheel guard, said shield comprising:

(a) a main plate, substantially normal to the movement of the grinding wheel, fixedly secured to the base, and having a front opening and a rearwardly extending top portion;

(b) at least one side cover, substantially parallel to the movement of the grinding wheel, fixedly but removably secured to the base and to the main plate, with said main plate and side cover being secured so as to be in telescoping relation with the grinding wheel guard; and

(c) a replaceable guard segment, fixedly but removably secured to the main plate and fitting partially within the main plate front opening, and having a predetermined opening therein to permit insertion of the workpiece to be ground, whereby said operatorprotective shield, by being fixedly secured to the machine base and in telescoping relation with the grinding wheel guard, in the event of grinding wheel failure, prevents broken wheel fragments from leaving the grinding machine and causing injury to the operator.

3. An operator-protective shield for a grinding machine having a base with ways and a movable wheelhead thereon for mounting a rotatable grinding wheel and a grinding wheel guard therefor, said shield comprising:

(a) a main plate, fixedly secured to the base substantially normal to the movement of the wheelhead, having a front opening;

(b) at least one side cover fixedly secured to the base,

substantially parallel to the movement of the wheelhead, with said main plate and side cover being secured so as to be in partially overlapping relation with the grinding wheel guard; and

(c) a replaceable guard segment, fixedly but removably secured to the main plate and fitting partially within the main plate front opening, and having an arcuate wall portion curved in approximate correspondency with the grinding wheel periphery, said arcuate wall portion having a definite size opening therein to permit insertion of at least part of the workpiece to be machined.

4. In a grinding machine (a) a base;

(b) a wheel slide mounting a grinding wheel and a guard therefor, with the guard substantially enclosing the grinding wheel;

(c) ways on the base supporting the wheel slide for translational movement relative to the work to be ground;

(d) a main frame fixedly secured to the base, substantially normal to the movement of the wheel slide and having a front opening therein;

(e) at least one side cover fixedly secured to the main frame, substantially parallel to the movement of the wheel slide, with said main frame and side plate being so positioned and secured to the base so as to be in telescoping relation with the grinding wheel guard regardless of the position of the wheel slide; and

(f) a replaceable guard segment fixedly but removably secured to the main frame and fitting partially within the main frame front opening, said replaceable insert having a substantially curved surface wall portion curved in approximate correspondency with the grinding wheel periphery, said wall portion having a predetermined opening therein to accommodate the requirements of a particular grinding wheel workpiece combination.

5. In a grinding machine (a) a base;

(b) a wheel slide mounting a grinding wheel and a guard therefor, with the guard substantially enclosing the grinding wheel;

(c) ways on the base supporting the wheel slide for translational movement relative to the work to be ground; and

(d) an operator-protective shield including:

(1) a main frame fixedly secured to the machine base, substantially normal to the movement of the grinding wheel slide, and having a front opening therein;

(2) at least one side cover fixedly secured to the main frame, substantially parallel to the movement of the grinding wheel slide, with said main frame and side plate being so positioned and secured to the base so as to be in telescopic relation with the grinding wheel guard regardless of the position of the grinding wheel slide; and

(3) a replaceable guard segment fixedly but removably secured to the main frame and fitting partially within the main frame front opening, said replaceable insert having an arcuate wall portion curved in approximate conformity with the grinding wheel periphery, said arcuate wall portion having a predetermined workpiece opening therein to accommodate particular grinding wheel and workpiece requirements, whereby said operator-protective shield, by being fixedly secured to the machine base and in telescoping relation with the grinding wheel guard, in the event of grinding wheel failure prevents broken wheel fragments from leaving the grinding machine and causing injury to the operator.

6. The grinding machine of claim 5 with the addition of a deflection member movably attached to said main frame for selectively covering and uncovering said predetermined workpiece opening in said replaceable guard segment.

7. The grinding machine of claim 6 wherein said deflection member covers said predetermined workpiece opening in said replaceable guard segment while the workpiece is being ground.

8. The grinding machine of claim 5 including a coolant line operatively connected to the replaceable guard segment of said operator-protective shield.

9. The grinding machine of claim 8 wherein said replaceable guard segment is provided with a passageway for coolant leading to said predetermined workpiece opening.

10. The grinding machine of claim 9 including a coolant nozzle to direct said coolant between the grinding wheel and the work to be ground.

11. The grinding machine of claim 5 wherein the lower portion of thearcuate wall portion of said replaceable guard segment is formed so as to channel broken wheel fragments, in the event of grinding wheel failure, into the base of the grinding machine.

12. The grinding machine of claim 11 wherein the base of the machine is also a coolant reservoir which, in the event of grinding wheel failure, will dissipate at least part of the energy of the broken wheel fragments being channeled thereto and help retain a substantial number of said wheel fragments.

13. The grinding machine of claim 12 wherein at least part of the top surface of said coolant reservoir consists of a yieldable cover means which in normal operation shields said reservoir from contaminants but which, in the event of grinding wheel failure, is pierceable by broken wheel fragments thereby absorbing at least part of the energy of said fragments and aiding in the retention of said fragments within said reservoir. 7 14. A guarding means for a high speed cutting tool used on a machine having a base with ways and a movable slide thereon for mounting said cutting tool for machining workpieces, said guarding means comprising in combination:

(a) a cutting tool guard, attached to the cutting tool slide, enveloping at least part of the periphery and sides of said cutting tool; and

(b) an operator-protective shield fixedly secured to said machine base, enveloping at least a complementary part of the periphery and sides of said cutting tool and having a definite size frontal opening therein to permit insertion of at least part of the workpieces to be machined, said cutting tool guard and operatorprotective shield being designed to be in telescoping relationship so as to substantially completely cover said cutting tool regardless of the position of the cutting tool slide with respect to said operatorprotective shield, whereby said operator-protective shield in conjunction with said cutting tool guard in the event of cutting tool failure prevents tool fragments from leaving said machine and causing injury to the operator.

15. A telescoping guard system for a grinding machine having a base with ways and a movable wheelhead thereon for mounting a rotatable grinding wheel for machining workpieces, said guard system comprising in combination: (a) a grinding wheel guard, attached to the movable wheelhead, enveloping at least a part of the periphery and sides of said grinding wheel; and (b) an operator-protective shield, fixedly secured to said machine base, enveloping at least a complementary part of the periphery and sides of said grinding wheel and having a definite size frontal opening therein to permit insertion of at least part of the workpiece to be ground, said grinding wheel guard and operator-protective shield being designed to be in telescoping relationship so as to substantially completely cover said grinding wheel regardless of the position of the movable wheelhead with respect to said operator-protective shield whereby said operator-protective shield in conjunction with said grinding wheel guard in the event of grinding wheel failure prevents broken wheel fragments from leaving the grinding machine and causing injury to the Operator.

References Cited UNITED STATES PATENTS 953,496 3/1910 Stone 51-269 1,116,658 11/1914 Willett 51269 LESTER M. SWINGLE, Primary Examiner 

